1. Field of the Invention
The present invention relates to a semiconductor device using a bipolar transistor.
2. Description of the Related Art
In recent years, the application fields of power devices have expanded dramatically. The power devices are increasingly applied to wide ranges of fields such as consumer products, transportation, and information in addition to the industrial use. Along with the progress toward high frequency and high efficiency in application, large current capability is required to the power devices, and at the same time various peripheral circuits such as protection circuits and drive circuits are indispensable. Accordingly, the development of products having higher functions and higher reliability is advancing through incorporation of those circuits into a single module.
An example of the protection circuits is an overheat protection circuit. The overheat protection circuit has a function of preventing breakage or deterioration of internal parts due to overheat caused by extraordinary rise in the temperature within the semiconductor integrated circuit. The overheat protection circuit includes a part that works as a temperature sensor which sends a signal thereof when the temperature reaches a certain value, and a part that works to receive the signal to make the circuit off.
Various elements are used as the temperature sensor portion. And, examples in which a bipolar transistor is used are disclosed in the following documents.    Patent Document 1: JP 2004-294322A    Patent Document 2: JP 10-122976A